Brain perfusion SPECT in patients with mild cognitive impairment and Alzheimer’s disease: comparison of a semiquantitative and a visual evaluation

Abstract

Due to the increasing importance of early recognition and differential diagnosis of dementias, cerebral perfusion scans using "single photon emission computed tomography" (SPECT) are increasingly integrated into the examination routine. The goal of this study was to check the diagnostic validity of SPECT scans of MCI- and DAT-patients, two subgroups out of 369 persons with etiologically unclear cognitive dysfunction, which underwent an assessment program for probable dementia including cognitive testing, cranial computed tomography, ultrasound, routine laboratory testing including vascular risk factors. After exclusion of patients with no or other forms of dementia we analyzed SPECT data of patients with mild cognitive impairment (MCI; n = 85) and dementia of the Alzheimer type (DAT; n = 78) in comparison with a healthy control group (n = 34).Visual assessment as well as a manual "regions of interest" (ROI) regionalization of the cortex were performed, whereby a ROI/cerebellum ratio was calculated as a semi-quantitative value. Association cortex areas were assessed regarding frontal, temporal, and parietal lobes of both hemispheres. When comparing the ratios of patients with DAT and controls, we found a statistically significant reduction of the cerebral perfusion in all measured cortex areas (p < 0.001). The comparison of patients with MCI with the selected control group also established a statistically significant difference in the cerebral perfusion for the evaluated cortex areas with the exception of the left hemispheric frontal and parietal cortex.A considerable number of the MCI patients showed an MMSE-score within the normal range, but with regard to the perfusion in the right hemispheric association cortex these patients also could be distinguished unambiguously from controls. Sensitivity levels found by visual assessment were at least as high as those found by the ROI method (pathological assessment: visual 49.4% vs. ROI 47.1% for MCI; visual 75.6% vs. ROI 73.1% for DAT). High experienced visual assessment of cerebral perfusion scans using SPECT provides an useful additional tool in diagnosis of cognitive impairment. The used semiquantitative ROI-method is nearly equivalent and does not depend on the experience of the investigator.

Framingham Cardiovascular Risk Profile Correlates with Impaired Hippocampal and Cortical Vasoreactivity to Hypercapnia

“…We offer that preexisting vessel impairment (independent of vascular risk, but possibly related to AD) had to be present to potentiate the influence of vascular risk factors on vessel expandability. Opposite to earlier findings (Dai et al, 2009;Staffen et al, 2006;Hirao et al, 2005;Caroli et al, 2007), CBF was not different between NL and MCI. Global CBF was, however, related to the global cognitive abilities as assessed with MMSE.…”

“…Resting CBF reductions are also well documented by single photon emission tomography in individuals with mild cognitive impairment (MCI) (Staffen et al, 2006;Hirao et al, 2005;Caroli et al, 2007). Furthermore, both CBF reduction (Hirao et al, 2005;Caroli et al, 2007;Hansson et al, 2009;Johnson et al, 1998;Kitagawa et al, 2009;Chao et al, 2010) and deficits in the reactivity of cerebral vessels to hypercapnia (vasoreactivity to hypercapnia (VR h )) forecast cognitive decline (Silvestrini et al, 2006).…”

CSF Biomarkers Correlate with Cerebral Blood Flow on SPECT in Healthy Elderly

“…In fact, several studies have reported rCBF decreases in the same frontal lobe location as in the current study, i.e. the superior posterior MFC [21,26,29,49,50]. In one of these studies, Caffarra et al [50] reported that all studied MCI subtypes had decreased rCBF in these regions, including individuals with dysexecutive MCI who also had the highest conversion rate to AD.…”

“…Hence, the findings in the current study differ in their locations. However, if CBF studies in early AD are examined in detail, it becomes evident that rCBF changes in many cases have also involved increases and decreases in the frontal lobe cortex [21,24,26,29,[48][49][50]. These areas have been reported as secondary findings and not highlighted as the more expected, concurrent posterior changes.…”

Visual Rating and ROI-Based Parametric Analysis of rCBF SPECT in Patients with Mild or Questionable Dementia: A Comparative Study

“…For visual ratings, as well as for parametric SPECT results, caution must be taken when interpreting the implication of an abnormal SPECT for the final diagnosis in a patient. As proposed recently in the revised research criteria [25] , SPECT (or PET) may be used as one of 3 biomarkers (diagnostic adjuncts) in the diagnosis of early AD in patients with confirmed episodic memory deficits.…”